fools2023/tools/decrypt_REPORT03.c

#define _GNU_SOURCE
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <string.h>

const uint8_t data[] = {
    0xfb, 0x72, 0x3a, 0x22, 0x21, 0x4b, 0x6a, 0xc2,
    0x28, 0xe6, 0xe4, 0xc1, 0xa7, 0x25, 0xb6, 0xe0,
    0x98, 0xb2, 0x0a, 0xe0, 0x9b, 0xab, 0xc1, 0x84,
    0xb8, 0x2d, 0x8f, 0xd8, 0x7e, 0x07, 0x3a, 0xcb,
    0xc9, 0xf0, 0xf5, 0x38, 0x51, 0x43, 0xed, 0x52,
    0xf8, 0x44, 0xe4, 0xc2, 0x50, 0x22, 0x27, 0x2a,
    0x65, 0x44, 0x81, 0x79, 0xc2, 0x6c, 0xb4, 0xaf,
    0xd9, 0x9d, 0x7c, 0x74, 0xb3, 0x58, 0xea, 0xcd,
    0x69, 0xe2, 0xa2, 0xdf, 0xe7, 0xca, 0xc4, 0x65,
    0xe0, 0xe8, 0xf3, 0xbe, 0xee, 0x97, 0x68, 0xad,
    0x61, 0x0e, 0x27, 0x78, 0x32, 0x86, 0x6d, 0x5c,
    0x02, 0xc2, 0x6e, 0xd1, 0xdf, 0x93, 0x14, 0x4d,
    0xcb, 0x1a, 0x90, 0xf4, 0x20, 0x95, 0xc0, 0xd3,
    0x1d, 0xe8, 0x73, 0x2b, 0xdb, 0xaf, 0xae, 0x74,
    0x7a, 0x1d, 0x50, 0x4a, 0xa6, 0x9d, 0x56, 0xcc,
    0xb5, 0x5d, 0x07, 0xd1, 0x04, 0xa7, 0x16, 0x5c,
    0x1d, 0x40, 0x4e, 0x65, 0x51, 0xf2, 0x68, 0x0a,
    0x4a, 0xb3, 0x56, 0x56, 0xc1, 0x51, 0x1f, 0x0f,
    0xc2, 0x7d, 0x4b, 0x29, 0x5b, 0x58, 0x1d, 0x2f,
    0xff, 0x66, 0xc0, 0x3c, 0xbb, 0xbb, 0x34, 0x93,
    0x30, 0xe6, 0x34, 0xb7, 0x8d, 0xd4, 0x4a, 0xa3,
    0xd7, 0x88, 0x00, 0x72, 0xba, 0x13, 0x0c, 0x4d,
    0x97, 0x46, 0xe0, 0xbb, 0x07, 0xa6, 0xef, 0xfa,
    0x12, 0x0a, 0xfe, 0x56, 0xe9, 0x14, 0x2b, 0xda,
    0x64, 0x3c, 0xfe, 0xc5, 0x3c, 0xa3, 0x50, 0x02,
    0x20, 0xb7, 0x20, 0x05, 0x3d, 0xdb, 0xf1, 0x8a,
    0x81, 0x41, 0x4c, 0x24, 0x52, 0x38, 0x8f, 0xb9,
    0x7e, 0x2e, 0x6f, 0x76, 0x1c, 0x3f, 0x97, 0x87,
    0x16, 0xd5, 0xd3, 0xc9, 0x70, 0x92, 0xd7, 0xd2,
    0x47, 0x59, 0xe6, 0x87, 0x12, 0x2c, 0xe0, 0xa5,
    0x6c, 0x17, 0x9c, 0xbe, 0xee, 0xe4, 0xd4, 0x50,
    0xea, 0x94, 0x57, 0x91, 0x4f, 0xb1, 0x57, 0xaa,
    0x46, 0xe9, 0x86, 0x76, 0xd3, 0xf8, 0xb9, 0xa5,
    0x8c, 0x9c, 0x57, 0x56, 0x0a, 0x72, 0x48, 0xc8,
    0x14, 0xb6, 0x8b, 0xf2, 0x48, 0x3c, 0x4d, 0xb5,
    0x3a, 0x48, 0x07, 0xa6, 0xf2, 0x8e, 0xa3, 0x0b,
    0x39, 0x02, 0x75, 0x9b, 0xc8, 0xdc, 0x6f, 0x0a,
    0x75, 0x00, 0x52, 0x6d, 0xbf, 0x77, 0x89, 0x2f,
    0xce, 0xb0, 0x27, 0xef, 0x42, 0x1e, 0x36, 0xe1,
    0x37, 0xc6, 0xf7, 0x77, 0x34, 0x1d, 0x6a, 0xd3,
    0xa7, 0x48, 0x6a, 0xc1, 0x7d, 0xe7, 0x76, 0x8c,
    0x62, 0x8f, 0x62, 0x8c, 0x5c, 0xe4, 0xf1, 0xf3,
    0xfd, 0x5f, 0xb6, 0x9d, 0xb4, 0xd7, 0xa8, 0xa0,
    0xcd, 0xde, 0x8b, 0x72, 0x73, 0xe4, 0xfa, 0xe7,
    0x33, 0x8f, 0x11, 0x1e, 0xaf, 0xd3, 0x40, 0xa7,
    0x86, 0x26, 0xf3, 0x77, 0x4c, 0x6e, 0x2d, 0x2d,
    0xa4, 0x03, 0xc2, 0x74, 0x2e, 0xb3, 0xdd, 0x85,
    0x29, 0x41, 0x90, 0xc3, 0xc7, 0x3a, 0x96, 0xb9,
    0x8e, 0x35, 0xcf, 0x37, 0xc0, 0xc8, 0xff, 0xd5,
    0x8b, 0x9f, 0xa1, 0xd9, 0x0f, 0x8e, 0x8e, 0xc6,
    0x11, 0xc1, 0xc0, 0xc9, 0x9e, 0x5b, 0x9c, 0xa1,
    0x2d, 0xc6, 0x4b, 0xf5, 0x34, 0x65, 0xb4, 0xcc,
    0xac, 0x88, 0xbf, 0x49, 0x43, 0x77, 0xac, 0x8f,
    0x61, 0x71, 0x8e, 0x59, 0x7f, 0x78, 0xd9, 0x73,
    0x41, 0x90, 0x73, 0x8b, 0x8e, 0x93, 0x3f, 0x6e,
    0xdd, 0x2e, 0x37, 0xe8, 0x72, 0x43, 0xa1, 0xf3,
    0xa9, 0xfe, 0x7f, 0x98, 0xf3, 0xa5, 0x98, 0x43,
    0xe5, 0x60, 0xb9, 0x5d, 0xbd, 0xba, 0x3f, 0xae,
    0x71, 0xf6, 0xed, 0xc1, 0xfe, 0x8f, 0x2d, 0x15,
    0xd9, 0xc6, 0xf7, 0x57, 0x83, 0x57, 0x7e, 0x10,
    0xb6, 0xc3, 0x76, 0x29, 0xb1, 0x10, 0x12, 0x1e,
    0xea, 0xa1, 0x15, 0x81, 0x9c, 0x22, 0x5f, 0x8a,
    0xf3, 0xff, 0x1c, 0x37, 0x4e, 0x57, 0x1b, 0x26,
    0x64, 0xb7, 0xca, 0x7c, 0xc8, 0x57, 0xd9, 0x57,
};

uint8_t dec[0x200];

void decrypt(uint16_t key)
{
    for (int i = 0; i < 0x200; i += 2) {
        key = (key * 0x41a7) ^ 0x5555;
        uint16_t d = data[i + 0] << 0 | data[i + 1] << 8;
        d ^= key;
        dec[i + 0] = d >> 0;
        dec[i + 1] = d >> 8;
    }
}

uint8_t fools[] = {'F', 'O', 'O', 'L', 'S'};

bool check()
{
    return memmem(dec, 0x200, fools, sizeof(fools));
}

uint16_t hash(char *str)
{
    uint16_t key = 0x9fc0;
    for (;;) {
        uint16_t in = str[0] << 0 | str[1] << 8;
        key = (((key * 2) ^ in) * 2) + in;
        if (*str == 0) break;
        str++;
        break;
    }
    return key;
}

int main()
{
    uint16_t key = 0;
    for (int i = 0xa4; i <= 0xffff; i++) {
        decrypt(i);
        if (check()) {
            fwrite(dec, 0x200, 1, stdout);
            key = i;
            break;
        }
    }
    printf("\n%04x\n", key);

    uint8_t str[16] = {0};
    for (;;) {
        int i;
        for (i = 0; i < 2; i++) {
            str[i]++;
            //if (str[i] >= 0x7b) {
                //str[i] = 0x20;
                //continue;
            //}
            //if (str[i] < 0x30) str[i] = 0x30;
            //if (str[i] >= 0x3A && str[i] <= 0x40) str[i] = 0x41;
            //if (str[i] >= 0x5B && str[i] <= 0x60) str[i] = 0x61;
            
            if (str[i] == 0x7f) {
                str[i] = 0x20;
                continue;
            }
            if (str[i] < 0x20) str[i] = 0x20;
            break;
        }
        if (i >= 2) break;

        if (key == hash(str)) {
            printf("%s\n", str);
        }
    }
}